1. Field
The disclosure relates to a sealed battery.
2. Description of Related Art
Lithium-ion secondary batteries, nickel-metal-hydride batteries, and other kinds of sealed secondary batteries have become increasingly important in recent years as power sources to be mounted in vehicles, and power sources for personal computers and portable terminals. Sealed lithium-ion secondary batteries, which are lightweight and have high energy density, are especially expected to be more widespread as high-output power sources mounted in vehicles.
A typical sealed battery includes a case having an opening portion, an electrode assembly accommodated in the case, and a lid welded to the opening portion of the case to seal the opening portion. The lid has through-holes extending through the lid in a thickness direction of the lid. The through-holes are spaces that open on the outer side of the lid, extend in the thickness direction of the lid to the backside of the lid (inner side of the lid on the inside of the battery), and open on the backside of the lid. The electrode assembly is electrically connected to collector terminals having portions that pass through the through-holes and project from the lid.
Each collector terminal may be fixed to the lid, for example, in the following method. A portion of the cylindrical collector terminal is passed through through-holes formed in an external terminal, an insulator, the lid, and an insulating seal (gasket), the portion of the terminal is projected from the through-holes, and then the top end of the projecting portion of the terminal is deformed such that the top end of the terminal expands radially outward with respect to the central axis of the projecting portion of the terminal (i.e. the projection portion is riveted). In this way, the collector terminal is fixed to the lid. The projecting portion that has expanded may be joined to the top surface of an external connection terminal by laser welding when needed. When the collector terminal is fixed to the lid in this method, the gasket provides sealing between the lid and the collector terminal. This makes it possible to prevent leakage of gas from the through-hole of the lid through which the collector terminal is passed, and to prevent a short-circuit between the collector terminal and the lid.
Such a sealing structure including a lid, collector terminals, and gaskets is described in each of Japanese Patent Application Publication No. 2014-7119 (JP 2014-7119 A), Japanese Patent Application Publication No. 2014-116139 (JP 2014-116139 A), Japanese Patent Application Publication No. 8-203494 (JP 8-203494 A), and Japanese Patent Application Publication 2012-182070 (JP 2012-182070 A). Each of these documents describes a sealing structure in which the bottom surface of a lid (i.e. the surface in contact with a gasket) is provided with a downward protrusion, so that a portion of the gasket is compressed. This structure further improves the sealability in the vicinity of a collector terminal.